The present invention relates to graft sulfonated polyesters, a method of preparing them and their application to sizing textile threads and fibers.
It is known to use sizing products in the textile industry, to improve the abrasion resistance of threads and fibers during weaving, the sizing products being eliminated with water after the weaving operation.
Aqueous dispersions or solutions of acrylic or more generally vinyl copolymers have been proposed for this purpose. It has been found that products of this type, and particularly those based on vinyl acetate, are not suitable for sizing all textile threads. For example, they have insufficient adhesion to threads based on polyesters.
Interesting products have been obtained by copolymerizing (meth)acrylic esters and (meth)acrylic acid in the presence of a water dispersible sulfonated polyester (Japanese applications published under numbers 34153/1975 and 201079/1986), for example from 30 to 60% of a water dispersible sulfonated polyester and 70 to 40% of a copolymer of (meth)acrylic esters and (meth)acrylic acids. However, these products have the drawback of being particularly expensive.
Applicants have made the surprising discovery that an effective sizing agent can be obtained (a) by considerably reducing the content of water dispersible sulfonated polyester and (b) by replacing most of the (meth)acrylic esters with, for example, vinyl acetate, which is far less expensive.